Lecture12 - ChE 210: Meeting 12 February 9,2011 Outline...

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Unformatted text preview: ChE 210: Meeting 12 February 9,2011 Outline (F&R Sections 4.6-4.7) Homework Due Friday 02/11/2011 - Reaction Terminology 4.32, 4.33, 4.35c-e, 4.37 - Material Balances on Reacting Processes - Degrees of Freedom in a Reacting Process Reaction Terminology (continued from Meeting 11) Extent of reaction (E) — moles converted from reactant to product, defined in terms of a single component of a reaction (typically a component with a stoichiometric coefficient of 1) Example: 2302+0292803 If a feed containing 50 moles of SOZ and 20 moles of 02, is reacted until only 5 moles of 02 remains, the extent of reaction is 15 moles (defined in terms of Oz) Equilibrium constant — the ratio of the concentration of products to reactants when a reaction has reached thermodynamic equilibrium Example: C2H6 + H20 9 CzH‘CHHz [Cglfl5OH] equilibrium constant(K)=Tff . ' CZH4 O] 1/7 ChE 210: Meeting 12 ‘ February 9, 2011 Yield — amount of product formed relative to the amount of product that would have formed if no undesired side reactions occurred Example: C2H6 + H20 9 CzH4ii+Ile [02%] yield = Selectivity — amount of desired product formed relative to undesired products Example: Csz + H20 9 Cszy‘x‘+}H2 C2H6 + H2 9 2 CH4 C2H4 + C2H5 9 C3H6 + CH4 V [02H4] [CH4] [02H4] selectivity: [C H ] 3 6 or selectivity = 2/7 ChE 210: Meeting 12 February 9, 2011 Material Balances on Reacting Processes (Handout) - Three types of material balances for a reacting process: molecular, atomic, extent of reaction - All balances start from general balance equation In + Generation — Out — Consumption = Accumulation - Molecular balances have the most unknowns and are typically avoided 3/7 Ease—mum we Ewen. £23022). :o_um_:.E:oo< u :03. E350 - 5:90:00 + "scum: .m. mocmfim 3.986 r N: + fmo ¢ fwo ngmo 6:; N: 5:: I 0 6:2 oow :_E\ I _0Ev_ 0v ChE 210: Meeting 12 Degrees of Freedom in a Reacting Process Molecular: unknowns 5 r i - ff.» molecular balances — (1 process specifications - L physical properties and laws - physical constraints a stoichiometric ratios J :1 \w / -~‘x7i! degrees of freedom 4/7 ' 7 , “(4:17” February 9, 2011 ChE 210: Meeting 12 February 9, 2011 Atomic: unknowns — atomic balances _ proceSs specifications - physical properties and laws - physical constraints degrees of freedom Extent of Reaction: unknowns in; - molecular balances - A process specifications - physical properties and laws - physical constraints degrees of freedom 5/7 ChE 210: Meeting 12 __T n2 =mol CCl4/s n1=mo|02/s 3.76n1=molN2/s n3 =mol02/s 3.76n3 = mol N2/s n4 =mol CCl4/s n5 =mol CCl4/s February 9, 2011 **If two molecular species are in the same ratio everywhere in a process, balances on those species are not independent “(v ,1 l l ~ é.» " **If two atomic species occur in the same ratio everywhere in a process, balances on those species are not independent /l4f‘ 6/7 ChE 210: Meeting 12 February 9, 2011 Example Problem 4.51 C;H4 + Hgo 9 CZFI’SOH - 1- 1: x -7 2C2H5OH 9 (C2H5)ZO + H20 “mm = 43.3mol ngout = 44.76mol n1,in = I n3,out = 2.5mol n4yout = 14 mol Out ninert,out = 9.3mol ‘ ninertjn =1 2 m) . :1 \'_, 141L311 \> “r .4 1 1 r ; ,; i k l \ T 7“ ;J\ ~\ KANKL‘V. i, \J' \_ if" \ \1 w ‘7 \z ’ ‘* ‘ "\ I'x:\ -‘ my \. ‘ -.‘ 1 *2. _ ‘ MALL: ,1” 1 GM UNA v“ ‘1 RN LU‘ ‘ h (xx ) fl 1“ ‘ ' ¥ ‘ \ 1‘ / r (W‘ J ‘1 \m‘ l ( , -. A r ., g \H “1.1, f 1 ’ 7 11 >2 2 x .\ ( K ‘ l 4| _ f\ \I, ,i W \ ’ } \411LV‘ \(‘\\; IVY !‘\3;-\.V £L/' hum K K- —\ 7/7 ...
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Lecture12 - ChE 210: Meeting 12 February 9,2011 Outline...

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